Panoramic imaging system
An optical imaging system and method for producing panoramic images exhibiting a substantial field of view.
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This application claims the benefit of U.S. Provisional Application No. 60/862,973 filed 25 Oct. 2006, the entire file wrapper contents of which are incorporated by reference as if set forth at length herein.
FIELD OF THE INVENTIONThis invention relates generally to the field of optical imaging and in particular to a composite panoramic imaging system that provides overlapping fields of view such that a composite image may encompass a full 360° field of view.
BACKGROUND OF THE INVENTIONIn a number of applications the ability to generate a panoramic image exhibiting a substantial field of view e.g., 360° is of great utility. Efforts to date that provide such panoramic images oftentimes involve complicated arrangements of multiple cameras, sophisticated image processing software or combinations thereof.
SUMMARY OF THE INVENTIONOne embodiment of the present invention provides a panoramic imaging system that produces a composite panoramic image exhibiting a substantial field of view, e.g., 360°. Advantageously a system constructed according to the present invention needs only a single image sensor to provide a panoramic image. In addition, a system so constructed according to the present invention may advantageously exhibit a substantially larger vertical field of view (VFOV) than prior art systems of comparable size.
In sharp contrast to the prior art multi-camera configurations, an apparatus constructed in accordance with the present invention does not merely reflect or redirect the fields-of-view of a plurality of imagers (cameras) as done in the prior art multi camera configurations. Rather, a reflective apparatus constructed according to the present invention is effectively a part of an imager's optical objective.
Viewed from a first aspect—the present invention is directed to an arrangement employing a pyramid with convex faces to provide a panoramic field of view to a camera or other imaging system.
Viewed from another aspect—the present invention is directed to an arrangement employing a pyramid immersed or suitably enveloped in a high refractive index transparent material such as glass or plastic to provide a panoramic field of view to a camera or other imaging system.
Viewed from still another aspect—the present invention is directed to a method of producing a panoramic image and images so constructed.
Viewed from yet another aspect—the present invention is directed to an encapsulated panoramic imaging system exhibiting a suitably small size, modest power requirement and panoramic imaging capability for numerous in-vivo applications.
A more complete understanding of the present invention may be realized by reference to the accompanying drawing in which:
The following merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope.
Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.
Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.
Thus, for example, it will be appreciated by those skilled in the art that the diagrams herein represent conceptual views of illustrative structures embodying the principles of the invention.
By way of further background and as known in the art, a panoramic imaging system may include a plurality of cameras with contiguous fields-of-view such that a composite image covers a full 360°. If each of the cameras shares a virtual center of perspective, then a seamless and natural-looking composite image can be formed without employing computationally intensive algorithms. For applications such as real-time video recording, transmission, and display, such low computational overhead is beneficial.
U.S. Pat. No. 5,745,305 describes such a panoramic viewing system in which several cameras have a common optical center (center of perspective). As described therein, the field of view (FOV) of each camera is redirected by one face of a reflective pyramid having 45° side inclination(s). If folded centers of perspective, lying on the optical axis folded by the mirrors, are positioned in a common plane with the pyramid apex, then the mirror-image optical centers are coincident.
An understanding of these principles may be enhanced with reference to
As recognized by those skilled in the art, the edges of the pyramid 110 in such a configuration cannot be made infinitely sharp. Consequently a portion of the HFOV is lost due to the finite radius of curvature, chamfer, or chipping on the edge.
U.S. Pat. Nos. 6,111,702 and 6,700,711 disclose one approach to eliminate the edges from the FOV whereby the folded centers of perspective are raised above the plane containing the apex of the pyramid such that the virtual optical centers (centers of perspective) are displaced outward from the center of the pyramid.
With that approach in mind and turning our attention now to
For large conjugate ratios (distantly viewed objects), the difference in parallax from a camera positioned at a particular center of perspective to a next camera positioned at the next center of perspective is negligible and any gaps are small relative to the overall scene dimensions (object height). For example, a 2 mm blind region may not be particularly noticeable when viewing a scene 100 m away.
For certain potentially useful applications of panoramic imaging systems such as endoscopes, capsule endoscopes, and boroscopes, however, the conjugate ratio is not particularly large as distant objects are not observed in these applications. More specifically, a conjugate ratio in such applications may be well under 100 or even under 10. For situations exhibiting a low conjugate ratio, any blind regions are no longer an unnoticeable fraction of the total object imaged. Compounding this is the fact that any difference in parallax is now more noticeable as well.
Turning our attention now to
For the example in
According to an aspect of the present invention, if Γ is decreased a larger vertical field of view is achievable with a physically smaller system.
Turning now to
With continued reference to that
As can be further observed from this
As can be appreciated by those skilled in the art, while the present invention has been shown specifically including a pyramid, the invention is not so limited. By way of additional example and not limitation, it is noted that a collection of reflective surfaces may be arranged such that their collective arrangement is substantially pyramidal in shape. In this manner, the same or different reflective surfaces may be employed, or different media having different (or the same) refractive index may further immerse the reflective structures. Advantageously, a different media may be used to immerse different reflective surfaces. As an illustration of these concepts,
Notwithstanding the above, finite edge regions may vignette at the edges of the HFOV. For example, in
As shown in this
Advantageously, the immersive medium (object) will act as a lens if either the first 901 or third 903 interfaces shown are curved. As shown in
By way of example, the VFOV is 50°, as in our prior-art example in
As can now be appreciated by those skilled in the art, an apparatus constructed accordion to the present invention does not merely reflect or redirect the fields-of-view of a plurality of imagers (cameras) as done in prior art multi camera configurations. Rather, an apparatus according to the present invention is effectively a part of each imager's (camera's) optical objective.
The angles of at least some of the rays, relative to the optical axis, immediately after reflection from a mirror are less than they are in at least a portion of the region between the optical imaging system and the subject object, wherein that portion includes the points where the FOVs of adjacent cameras first overlap. In particular, if the mirror faces are curved, or if the material immersing the pyramid has curvature on either the first or second surface, or both, then the apparatus has optical power and must be considered an integral part of the objective. Finally, all optical systems may be used in reverse as projection systems.
An exemplary compact panoramic imaging system according to the principles of the present invention is shown in as a cross-sectional schematic in
As may be further appreciated, devices such as those shown in
Such a device was described in U.S. patent application Ser. No. 11/642,275 for an “In Vivo Sensor With Panoramic Camera” filed Dec. 19, 2006 assigned to the assignee of the present invention and is incorporated herein by reference.
With reference to
As shown in
At this point, while I have discussed and described my invention using some specific examples, those skilled in the art will recognize that my teachings are not so limited. More specifically, while all examples presented herein use four-sided pyramids, the number of sides could, in principle, be any number greater than one. Also, the inclination of the faces need not be exactly 45°. In addition, and while not specifically illustrated, an immersed reflector configuration having convex mirror faces may be constructed. Also, the reflective surface clear apertures need only be coincident with the faces of a pyramid (or convex-faced pyramid, as described above) and the physical object or objects that these reflective surfaces reside on need not be pyramidal. Finally, a system constructed according to the principles of the present invention may advantageously off-load, or otherwise transmit component images to other systems (i.e., not in-vivo) for subsequent processing and/or assembly into panoramic or other images.
Accordingly, the invention should be only limited by the scope of the claims attached hereto
Claims
1. A panoramic imaging system comprising:
- a plurality of image capture devices, each having an associated center of perspective; and
- a pyramidal reflective element having a plurality of reflective side facets facing in different directions wherein each one of the reflective side facets folds an optical axis associated with at least one of the image capture devices; wherein each one of the centers of perspective has associated with it a component image wherein the component images associated with adjacent side facets partially overlap;
- such that said component images may be combined into a composite panoramic image and
- one or more immersion media into which the reflective side facets of the pyramidal reflective element are effectively immersed, said immersion media having a characteristic index of refraction n1;
- a further medium into which the immersion media are effectively immersed, said further medium having a characteristic index of refraction n2, wherein n1>n2 for each immersion medium;
- wherein said imaging system includes a plurality of optical paths each of which includes: a first refractive interface through which a light ray is bent by a first angular amount followed by; a reflective interface followed by; a second refractive interface through which the light ray is bent by a second angular amount.
2. The panoramic imaging system of claim 1 wherein said second angular amount is less than or equal to said first angular amount.
3. The panoramic imaging system of claim 1 further comprising an image processing device for combining the component images into a composite panoramic image.
4. The panoramic imaging system of claim 1 wherein one or more of said reflective side facets exhibits a convex shape.
5. A panoramic imaging system comprising: such that said component images may be combined into a composite panoramic image and
- a plurality of image capture devices, each having an associated center of perspective; and
- a plurality of reflective surfaces facing in different directions wherein the reflective surfaces are arranged such that their combined shape is substantially pyramidal wherein each one of the reflective surfaces folds an optical axis associated with at least one of the image capture devices; wherein each one of the centers of perspective has associated with it a component image wherein the component images associated with adjacent side facets partially overlap;
- one or more immersion media into which the reflective side facets of the pyramidal reflective element are effectively immersed, said immersion media having a characteristic index of refraction n1;
- a further medium into which the immersion media are effectively immersed, said further medium having a characteristic index of refraction n2, wherein n1>n2 for each immersion medium;
- wherein said imaging system includes a plurality of optical paths each of which includes: a first refractive interface through which a light ray is bent by a first angular amount followed by; a reflective interface followed by; a second refractive interface through which the light ray is bent by a second angular amount.
6. The panoramic imaging system of claim 5 wherein each one of said component images is formed on a common image plane.
7. The panoramic imaging system of claim 6 wherein at least a portion of the image capture devices lie on the common image plane.
8. The panoramic imaging system of claim 5 further comprising an image processing device for combining the component images into a composite panoramic image.
9. The panoramic imaging system of claim 5 wherein one or more of said reflective surfaces exhibits a convex shape.
10. A method of producing a composite panoramic image using a plurality of sensors each having a respective center of perspective and each center of perspective being associated with a particular optical axis, said method comprising the steps of: wherein for each center of perspective there is associated one or more individual light rays that are refracted in the first refractive step by a first angular amount and refracted in the second refractive step by a second refractive angular amount wherein the first angular amount is greater than the second angular amount.
- for each of the plurality of centers of perspective refracting light corresponding to a particular center of perspective; redirecting the refracted light by folding the optical axis associated with the refracted light; further refracting the redirected light; and generating a component image from the further refracted light; and merging the plurality of component images so generated into a panoramic image;
20050151837 | July 14, 2005 | Cutler |
20060217593 | September 28, 2006 | Gilad et al. |
Type: Grant
Filed: Jan 17, 2007
Date of Patent: Oct 19, 2010
Patent Publication Number: 20080100928
Assignee: Capsovision Inc. (Saratoga, CA)
Inventor: Gordon Cook Wilson (San Francisco, CA)
Primary Examiner: Alicia M Harrington
Attorney: Brosemer, Kolefas & Associates
Application Number: 11/624,209
International Classification: G02B 13/06 (20060101); G02B 5/04 (20060101);